6Li content may be as low as 3.75% in natural samples. 7Li would therefore have a content of up to 96.25%.

References

Lithium ( IPA: /ˈlɪθiəm/, from Greek: lithos: stone, because it was discovered in petalite) is a chemical element with the symbol Li and atomic number 3. Lithium is one of only four elements theorized to have been created in the first three minutes of the universe through a process called Big Bang nucleosynthesis. It is in group 1 of the periodic table, among the alkali metals and is the lightest solid element.

Lithium in its pure form does not occur naturally on Earth. It is a soft, silver white metal. Lithium reacts with oxygen from the air to form black lithium oxide (Li2O). It therefore has to be stored under the cover of oil to stop this oxidation reaction from occurring. It tarnishes and oxidizes very rapidly in air and water. Lithium metal is used primarily in heat-transfer applications, batteries (mainly cell phone and camera batteries), household appliances such as toasters and microwaves, and in high performance alloys such as those used for aircraft construction. Lithium compounds are used pharmacologically as a class of mood stabilizing drugs, a neurological effect of the lithium ion Li+.

Basic features

Though in group 1, lithium also exhibits properties of the alkaline-Earth metals in group 2. Like all alkali metals, it has a single valence electron, and will readily lose this electron to become a positive ion. Because of this, lithium reacts easily with water and does not occur as the free element on Earth. Nevertheless, it is less reactive than the chemically similar sodium.

Lithium is soft enough to be cut with a knife, though this is significantly more difficult to do than cutting sodium. The fresh metal is silver in colour, rapidly tarnishing black in air. Lithium has only about half the specific gravity of water, giving solid metal lithium sticks the odd heft of a very light wood, such as balsa. The metal floats highly in hydrocarbons due to its low density, and jars of lithium in the laboratory are typically composed of black-coated sticks held down in hydrocarbon mechanically by the lid of the jar and other sticks.

When placed over a flame, lithium gives off a striking crimson colour, but when it burns strongly, the flame becomes a brilliant white. Lithium will ignite and burn when exposed to water and water vapors in oxygen. It is the only metal that reacts with nitrogen at room temperature. Lithium has a high specific heat capacity, 3582 J/(kg·K), and a great temperature range in its liquid form, which makes it a useful chemical.

Lithium metal is flammable and potentially explosive when exposed to air and especially water, though it is far less dangerous than other alkali metals in this regard. The lithium-water reaction at normal temperatures is brisk but not violent. Lithium fires are difficult to extinguish, requiring special chemicals designed to smother them.

Lithium metal is a corrosive and requires special handling to avoid skin contact. The metal itself is usually less a handling hazard than the caustic hydroxide produced when it is in contact with moisture. Lithium should be stored in a non-reactive compound such as naphtha or a hydrocarbon.

In humans lithium compounds apparently play no natural biological role, and are considered to be slightly toxic. Humans aside, lithium appears to be an essential trace element for goats, and possibly rats. When used as a drug, blood concentrations of Li+ must be carefully monitored.

Occurrence

Lithium pellets (covered in white lithium hydroxide)

On Earth, lithium is widely distributed, but because of its reactivity does not occur in its free form. In keeping with the origin of its name, lithium forms a minor part of almost all igneous rocks and is also found in many natural brines. Lithium is the thirty-first most abundant element, contained particularly in the minerals spodumene, lepidolite, petalite, and amblygonite. On average, Earth's crust contains 65 parts per million (ppm) lithium.

Since the end of World War II, lithium metal production has greatly increased. The metal is separated from other elements in igneous mineral such as those above, and is also extracted from the water of mineral springs.

The metal is produced electrolytically from a mixture of fused lithium and potassium chloride. In 1998 it was about US$ 43 per pound ($95 per kg). Chile is currently the leading lithium metal producer in the world, with Argentina next. Both countries recover the lithium from brine pools. In the United States lithium is similarly recovered from brine pools in Nevada.

Isotopes

Naturally occurring lithium is composed of 2 stable isotopes 6Li and 7Li with 7Li being the most abundant (92.5% natural abundance). Seven radioisotopes have been characterized with the most stable being 8Li with a half-life of 838 ms and 9Li with a half-life of 178.3 ms. All of the remaining radioactive isotopes have half-lifes that are less than 8.6 ms. The shortest-lived isotope of lithium is 4Li which decays through proton emission and has a half-life of 7.58043x10-23 s.

7Li is one of the primordial elements or more properly, primordial isotopes, produced in Big Bang nucleosynthesis (a small amount of 6Li is also produced in stars). Lithium isotopes fractionate substantially during a wide variety of natural processes, including mineral formation (chemical precipitation), metabolism, and ion exchange. Lithium ion substitutes for magnesium and iron in octahedral sites in clay minerals, where 6Li is preferred over 7Li, resulting in enrichment of the light isotope in processes of hyperfiltration and rock alteration.

An interesting isotope is the extremely unstable 11Li , that exhibits a Nuclear halo of two neutrons.

History

Petalite, which contains lithium, was first discovered by the Brazilian scientist José Bonifácio de Andrade e Silva toward the end of the 1700s on a trip to Sweden. Lithium was discovered by Johan August Arfwedson in 1817. Arfwedson found the new element within the minerals spodumene and lepidolite in a petalite ore, LiAl(Si2O5)2, he was analyzing during a routine investigation of some minerals from a mine on the island Utö in Sweden. In 1818 Christian Gmelin was the first to observe that lithium salts give a bright red colour in flame. Both men tried and failed to isolate the element from its salts.

The element was not isolated until William Thomas Brande and Sir Humphry Davy later used electrolysis on lithium oxide in 1818. Bunsen and Matiessen isolated larger quantities of the metal by electrolysis of lithium chloride in 1855. Commercial production of lithium metal was achieved in 1923 by the German company Metallgesellschaft through using electrolysis of molten lithium chloride and potassium chloride. It was apparently given the name "lithium" ( Greek λιθoς (lithos), meaning "stone") because it was discovered from a mineral while other common alkali metals were first discovered from plant tissue.

Applications

Because of its specific heat capacity, the largest of any solid, lithium is used in heat transfer applications. It is also an important battery anode material, used in lithium ion batteries due to its high electrochemical potential. In addition to being lighter than the standard dry cell, these batteries produce a higher voltage (3 volts versus 1.5 volts). Large quantities of lithium are used in the manufacture of organolithium reagents, especially n-butyllithium which has many uses in fine chemical and polymer synthesis.

Medical Use

Lithium salts such as lithium carbonate (Li2CO3), lithium citrate, and lithium orotate are mood stabilizers. They are used in the treatment of bipolar disorder, since unlike most other mood altering drugs, they counteract both mania and depression. Lithium can also be used to augment other antidepressant drugs. It is also sometimes prescribed as a preventive treatment for migraine disease and cluster headaches.

The active principle in these salts is the lithium ion Li+, which interacts with the normal function of sodium ion to produce numerous changes in the neurotransmitter activity of the brain. Therapeutically useful amounts of lithium are only slightly lower than toxic amounts, so the blood levels of lithium must be carefully monitored during such treatment.

Other uses

Lithium chloride and lithium bromide are extremely hygroscopic and frequently used as desiccants.

Lithium stearate is a common all-purpose high-temperature lubricant.

Lithium is an alloying agent used to synthesize organic compounds.

Lithium is used as a flux to promote the fusing of metals during welding and soldering. It also eliminates the forming of oxides during welding by absorbing impurities. This fusing quality is also important as a flux for producing ceramics, enamels, and glass.

Lithium is sometimes used in glasses and ceramics including the glass for the 200-inch (5.08 m) telescope at Mt. Palomar.

Lithium niobate is used extensively in telecommunication products, such as mobile phones and optical modulators.

The high non-linearity of lithium niobate also makes a good choice for non-linear optics applications.

Lithium deuteride was the fusion fuel of choice in early versions of the hydrogen bomb. When bombarded by neutrons, both 6Li and 7Li produce tritium. Tritium fuses with deuterium in a fusion reaction that is relatively easy to achieve. Although details remain secret, lithium apparently no longer plays a role in modern nuclear weapons, having been replaced entirely for the purpose by elemental tritium, which is lighter and easier to handle than lithium salts.

Lithium is used as a source for alpha particles, or helium nuclei. When 7Li is bombarded by accelerated protons, 8Be is formed, which undergoes spontaneous fission to form two alpha particles. This was the first man-made nuclear reaction, produced by Cockroft and Walton in 1929.

Lithium hydroxide (LiOH) is an important compound of lithium obtained from lithium carbonate (Li2CO3). It is a strong base, and when heated with a fat, it produces a lithium soap. Lithium soap has the ability to thicken oils and so is used commercially to manufacture lubricating greases.

Lithium metal is used as a catalyst in some types of methamphetamine production, particularly in illegal amateur “meth labs.”

Lithium hydroxide is an efficient and lightweight purifier of air. In confined areas, such as aboard spacecraft and submarines, the concentration of carbon dioxide can approach unhealthy or toxic levels. Lithium hydroxide absorbs the carbon dioxide from the air by reacting with it to form lithium carbonate. Any alkali hydroxide will absorb CO2, but lithium hydroxide is preferred, especially in spacecraft applications, because of the low formula weight conferred by the lithium. Even better materials for this purpose include lithium peroxide (Li2O2) and lithium superoxide (LiO2) that, in presence of moisture, not only absorb carbon dioxide to form lithium carbonate, also release oxygen. E.g. 4 LiO2 + 2CO2 --> 2Li2CO3 + 3 O2.

Market trend

Prices of lithium carbonate rose by 20% in 2005 and growth of up to 25% is forecast by Roskill Consulting Group for 2006, bringing prices back to the peak levels seen prior to SQM's entry into the market in 1996. New capacity due on-stream in Chile, Argentina and China is forecast to alleviate the upward pressure on prices after 2007.

Consumption of lithium increased by 4–5% per year between 2002 and 2005, driven by demand in lithium secondary batteries. Batteries accounted for 20% of total consumption in 2005, a rise from under 10% in 2000.

Continued expansion in the portable electronic products market and commercialisation of hybrid electric vehicles using lithium batteries suggest growth of up to 10% per year in lithium carbonate consumption in this market through 2010.

Between 2002 and 2005, lithium minerals production rose by 7% per year to reach 18,800 tonnes Li. Chile and Australia account for over 60% of total output. FMC Lithium of the USA, Chemetall of Germany and SQM of Chile continue to dominate production of downstream lithium chemicals.

China may emerge as a significant producer of brine-based lithium carbonate towards the end of this decade. Potential capacity of up to 45,000 tonnes per year could come on-stream if projects in Qinghai province and Tibet proceed.

Regulation

Some jurisdictions limit the sale of lithium batteries, which are the most readily available source of lithium metal for ordinary consumers. Lithium can be used to reduce pseudoephedrine and ephedrine to methamphetamine in the Birch reduction method, which employs solutions of alkali metals dissolved in anhydrous ammonia. However, the effectiveness of such restrictions in controlling illegal production of methamphetamine remains indeterminate and controversial.

Carriage and shipment of some kinds of lithium batteries may be prohibited aboard certain types of transportation (particularly aircraft), because of the ability of most types of lithium batteries to fully discharge very rapidly when short-circuited, leading to overheating and possible explosion. However, most consumer lithium batteries have thermal overload protection built-in to prevent this type of incident, or their design inherently limits short-circuit currents.

Lithium is a component for thermonuclear weapons (so called "hydrogen bombs") and applications of lithium for this purpose in the nuclear weapons industry is pursued in developing nuclear powers like India, and presumably others.

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